Yongzhao Yan Wipf Group Current Literature 9-5-2014
An Efficient Strategy Single-Electron-Transfer-Induced Tandem Anion–Radical Reactions
Frantisˇek Kafka, Martin Holan, Denisa Hidasovμ, Radek Pohl, Ivana Císarˇova,
Blanka Klepetμrˇovμ, and Ullrich Jahn*Angew. Chem. Int. Ed. 2014, 53, 9944 –9948
DOI: 10.1002/anie.201403776
Fe Fe+
NO
N+
O PF6-
PF6-
Nu- Nu
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SET-Mediated Transformation
✤ Radicals are generated from neutral precursors.
✤ Overall reactions are classified as neutral, oxidative and reductive.
✤ Stoichiometric amounts of SET agents.
1. Top. Curr. Chem. 2012, 320, 121–452
主要是oxi reduc两步set最后产生中性的产物
alkyl halides or sulfur electrophiles,
transition-metal-catalyzed atom-transfer radical reactions,
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Catalytic SET-Mediated Reactions✤ Reductive Titanium(III)-catalyzed reaction
1. Top. Curr. Chem. 2012, 320, 121–452
Ti promotes 2 SET
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Catalytic SET-Mediated Reactions
1. Org. Lett., 2008, 10 (19), pp 4383–4386
✤ Reductive Titanium(III)-catalyzed reactionjohn maciejsikiindoline scaffold synthesis
3mol%
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Catalytic SET-Mediated Reactions
1. Org. Lett., 2008, 10 (19), pp 4383–4386
✤ Reductive Titanium(III)-catalyzed reactiontrace O2 or H+ oxidize back
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Catalytic SET-Mediated Reactions✤ Ru(II) catalyzed photoredox reactions
1. Top. Curr. Chem. 2012, 320, 121–452
cat
cat
cat. = Ru(bipy)3Cl2
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Ferrocene/Ferrocenium Couple
1. Chem. Rev. 1996, 96, 877−910
mild Oxidantweak reductantrecommended by IUPAC for standard
0.40 V in MeCN
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Ferrocene/TEMPO Combination
1. Tetrahedron 2009, 65, 10917–10929
crappy yield in one-pothighest yield = 65%both 3 and 4 are used with 1 equiv.
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Ferrocene/TEMPO Combination
1. Tetrahedron 2009, 65, 10917–10929
Radical recombination faster than radical addition to alkene
without FeCp2
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1. Chem. Eur. J. 2009, 15, 58-62
Applications in Total Synthesis✤ Total Synthesis of 15-F2t-Isoprostane
✤ 39% desired isomer
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1. Tetrahedron 68 (2012) 1521-1539
Trapping Reagents
✤ CuCl2 and CuBr2 as oxidizing/trapping reagent
CuBr2 gave pdt with low stereoselectivity
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Ferrocene/TEMPO Redox Pair
Fe Fe+
NO
N+
O PF6-
PF6-
Nu- Nu
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all 2 3 trans 34 cis Ferrocene 1-10%
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Tandem Michael Addition/Radical Cyclization/Oxygenation Reactions
5 mol% 2 add TEMPO in the system to start with10a sele EWG sizetrans ewg and R1 major
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Tandem Michael Addition/Radical Cyclization/Oxygenation Reactions
5 exo to 6 endo
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Ferrocene/TEMPO Redox Pair
✤ Comparing with 52% and 47% (6:1)1
1. Eur. J. Org. Chem. 2012, 4461–4482
same distribution catalytic worked!
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TMP As Alcohol Protecting Group
1. Eur. J. Org. Chem. 2012, 4461–4482
Tolerance with reduction Zn cleavagemcpba directly oxidize it back
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Conclusion
✤ High stereoselectivity on several examples.
✤ TEMPO as a alcohol protecting group saving a protection step/excessive oxidant usage.
✤ Potentials in total synthesis
✤ SET oxidation by Ferroceium and combination with TEMPO
inseparable materialsONLY TEMPO?
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